The Research And Development Of Net3DBrowser IGES Postprocessor

In the society with highly developed information technology, the application of network is popularized increasingly, and the mankind society is entering network society. The emergence and development of Internet lessen the time-distance sense during the course of people's information communication, and a super time-distance society is gradually formed which enable people share separatly located information in real time. The diversified information services based on network occur endlessly, such as the remote education and training, the remote consultation, the shopping by network, netmeeting and so on. The shared information in these network services includes multimedia information such as text, data, video, sound, image and graphics and so on, thereinto, the CAD graphics data of products are also shared information applied widely. So it is of apparent society and application value to research and develop a 3D graphics browser based on network.NetSDbrowser, a 3D graphics browser based on network, is composed of two function modules: IGES postprocessor and rendering and interaction module supported by OpenGL, which constitute function plug-in modules of the 3D graphics browser embedded in the WebEx netmeeting.The development of Net3DBrowser IGES postprocessor is mainly discussed in the dissertation, including the following aspects:1. Analyze IGES files and extract graphics data. By studying the IGES data exchange standard and analyzing IGES files produced by the preprocessors of CAD systems, comprehend basic line elements and basic face elements constituting parts and summarize the means to get data information of parts and assemblies.2. Set up assembly tree view. Analyze necessary data information constituting assembly tree view and comprehend the representation rules of those data information in IGES files. According to these rules, the nodes of parts and assemblies are defined. To avoid the data redundance and insure the data integrity, the corresponding rules of getting the assembly tree view data are established.3. The convex decomposition of arbitrary planar polygon. As to simple concave polygons or complicated planar polygons with holes, they must be decomposed to the collection of triangular facets or arbitrary convex polygons to satisfy the requirement of succeeding graphic operations. After deeply studying current relative algorithms, and adopting the ideas of advanced decomposition algorithms, a convex decomposition algorithm for arbitrary planar polygons is put forward in the dissertation, which is basedon the algorithm of nearest bridging and the ideas of second bridging and loop division.Based on the above, the author implements NetSDBrowser IGES postprocessor on the Unix, Linux, Windows 9x/NT/2000 by utilizing C++.